Dynamic muffler

ABSTRACT

A muffler of simplified construction which compensates for variations in exhaust gas pressure and flow rate in order to eliminate back pressure from the muffler has a chamber in the form of a closed loop path having a given cross-sectional area. An inlet to the chamber and an outlet from the chamber are provided for the exhaust gas. A plurality of objects, such as hollow metal balls, dimensioned to substantially encompass the cross-sectional area of the closed loop path are movable around the path in response to force exerted by the exhaust gas. The spacing among the objects as they move around the path varies to compensate for changes in the exhaust gas pressure and flow rate, thus eliminating back pressure to an engine from the muffler.

United States Patent [191 Harrigan [4 1 May 27, 1975 DYNAMIC MUFFLER [76] Inventor: Roy M. Harrigan, Bromley Mountain Rd., Manchester, Vt. 05254 [22] Filed: Apr. 10, 1974 21 Appl. No.: 459,775

[52] US. Cl. 181/49; 181/64 R [51] Int. Cl. F0ln H08 [58] Field of Search 181/57, 58, 61, 63, 64 R, 181/64 A, 64 B, 49, 50, 71

[56] References Cited UNITED STATES PATENTS 971,424 9/1910 Werner 181/64 R 1,618,451 2/1927 Leary 181/64 R 2,764,250 /1956 .leffords 1 181/57 X 3,323,614 6/1967 Thrasher 181/64 R X 3,704,763 12/1972 Becker et a1 181/57 X Primary Examiner-Stephen J. Tomsky Assistant Examiner-John F. Gonzales Attorney, Agent, or Firm willis E. Higgins [57] ABSTRACT A muffler of simplified construction which compensates for variations in exhaust gas pressure and flow rate in order to eliminate back pressure from the muffler has a chamber in the form of a closed loop path having a given cross-sectional area. An inlet to the chamber and an outlet from the chamber are provided for the exhaust gas. A plurality of objects, such as hollow metal balls, dimensioned to substantially encompass the cross-sectional area of the closed 100p path are movable around the path in response to force exerted by the exhaust gas. The spacing among the objects as they move around the path varies to compensate for changes in the exhaust gas pressure and flow rate, thus eliminating back pressure to an engine from the muffler.

12 Claims, 4 Drawing Figures DYNAMIC MUFFLER FIELD OF THE INVENTION This invention relates to a muffler of the type in which movable members are utilized to deaden sound accompanying an exhaust gas, as well as to reduce or eliminate back pressure to an engine from the exhaust gas as it passes through the muffler. The invention further relates to such a muffler in which bearings for the movable members are not required. In its preferred form, the invention relates to such a muffler in which the relative position of the movable members varies to compensate for changes in the exhaust gas stream. While much of the following discussion deal with the environment of an internal combustion engine, it should be recognized that a muffler in accordance with this invention is suitable for use with essentially any exhaust gas stream accompanied by noise, such as that of steam engines, vacuum cleaners, pneumatic hammers, and the like.

DESCRIPTION OF THE PRIOR ART Mufflers of the type in which movable members activated by an exhaust gas stream are used for the purpose of deadening sound accompanying the gas stream are known in the art. For example, US. Pat. Nos. 771,070; 788,313; 1,110,512; 1,191,902 and 1,618,451 disclose such mufflers. As disclosed in these patents, such movable members have hitherto taken the form of turbine structures, in which impingement of the exhaust gas stream on the vanes of the turbine cause it to rotate. As discussed in the US. Pat. No. 1,618,451, the motion of the turbine structure helps to reduce back pressure to an engine, and the positioning of the vanes of the turbine between the exhaust gas inlet and outlet of the muffler serves to deaden sound accompanying the exhaust gas stream by reflecting it back to its source very effectively.

A significant problem associated with such dynamic mufflers which has hitherto hindered their large scale commercial acceptance is that turbine-type structures require some form of bearings for support. In a muffler environment, the provisions of bearings is disadvantageous due to the high heat and corrosive nature of most exhaust gas streams. This environment is an extremely demanding one for bearings. Their reliability is therefore a problem in a muffler.

While such mufflers are apparently effective for eliminating a great deal of back pressure from an exhaust gas stream as it passes through the muffler, variations in a typical internal combustion engine exhaust gas stream, both in terms of pressure and flow rate, are quite complex. In a turbine-type structure, the vanes of the turbine are fixed in their distance relationship to each other. This fixed relationship among the vanes limits the ability of such a dynamic muffler to compensate for all variations in an exhaust gas stream. Some back pressure is therefore developed in many exhaust gas streams as they pass through prior art dynamic mufflers.

Thus, while the muffler art is a well developed one, a need remains to increase the reliability of prior art dynamic mufflers, and to increase their ability to compensate for variations in exhaust gas streams.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a muffler of the type wherein movable members provide the primary sound deadening effect in which bearings for the movable members are not required.

It is a further object of this invention to provide a muffler of simplified construction which is effective against noise accompanying exhaust gases and has little or no back pressure.

It is still another object of the invention to provide a muffler of simplified construction which compensates for variations in pressure and flow of an exhaust gas stream, thereby to eliminate back pressure.

The attainment of these and related objects may be achieved through the use of the novel muffler herein disclosed. The muffler has a chamber which includes at least one closed loop path having a given crosssectional area. An inlet to the chamber for exhaust gas, and an outlet from the chamber for the exhaust gas are provided. A plurality of objects in the chamber are freely movable around the closed loop path in response to force exerted by the exhaust gas as it passes through the chamber from the inlet to the outlet. These objects are dimensioned to substantially encompass the crosssectional area of the closed loop path. For optimum sound deadening, a sufficient number of the objects should be provided to allow at least one of the objects to be positioned in each direction of travel around the closed loop path between the inlet and the outlet for the gas stream. This can be accomplished by a single, annular closed loop path containing, for example, from three to six spherical objects having just sufficient clearance in the closed loop path to permit their free movement around the path from the force of the exhaust gas. Alternatively, a number of closed loop paths can be provided, connected in series by their inlets and outlets, with each closed loop path containing a lesser number of the objects, even one per closed loop path, if desired. With such an arrangement, at least one of the objects inat least one of the closed loop paths will always block passage of sound from the inlet of the first closed loop path to the outlet of the last closed loop path.

The attainment of the foregoing objects, advantages and features of the invention should be apparent after review of the following detailed description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a plan view of a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the drawings, more particularly to FIGS. 1 and 2, there is shown a dynamic muffler in accordance with the invention. The muffler has a chamber 10, the walls 12 of which form a closed loop path having a given cross-sectional area, as best shown in FIG. 2. Exhaust gas inlet 14 is connected to chamber by means of Opening 16 and is positioned to deliver exhaust gas stream 18 tangentially to the closed loop path chamber 10. Exhaust gas outlet 20 is similarly connected to the chamber 10 in a tangential relationship by means of opening 22. Vanes 23 in openings 16 and 22 help to direct the exhaust gas stream 18, but they may be omitted if desired. Inside the chamber 10 is a plurality of hollow metal spheres 24 which are dimensioned to substantially encompass the crosssectional area of the closed loop path chamber 10, yet be free to move around the chamber 10 in response to forces exerted by the exhaust gas stream 18. In FIG. 1, five metal spheres 24 are shown, but it should be understood that a greater or lesser number could be employed. For optimum, continuous sound deadening with the muffler, at least one of the spheres 24 should be positioned between inlet opening 16 and outlet opening 22 in both the clockwise and counterclockwise directions, in order to reflect sound back toward its source at all times. For this purpose, it is contemplated that at least three spheres 24 should be used. The use of more than six spheres does not appear to add any substantial increase to the effectiveness of the sound deadening properties of the muffler, but a greater number may be employed in order to minimize discontinuities in the weight distribution of the spheres as they move around the chamber 10. Since the spheres 24 are propelled around the chamber 10 by the force exerted on them by exhaust gas stream 18, they are preferably made of a lightweight metal, such as aluminum or magnesium. Chamber 10 and exhaust gas inlet and outlet 14 and 20 may be fabricated of any suitable metal, such as corrosion resistant steel. In certain applications, such as with a vacuum cleaner, the muffler and spheres may be fabricated of a suitable plastic.

In use, exhaust gas inlet 14 is connected to the exhaust manifold (not shown) of an internal combustion engine, or other source of exhaust gas stream 18 accompanied by noise to be deadened. Exhaust gas stream 18 enters chamber 10 through inlet opening 16 and applies a force to sphere 24 located in the exhaust gas stream 18 between inlet opening 16 and outlet opening 22. This force propels the sphere around the closed loop path of chamber 10 in a clockwise direction. The presence of a sphere 24 between inlet opening 16 and outlet opening 22 in each direction deadens sound accompanying the exhaust gas stream 18 by reflecting it back toward its source. As the sphere 24 moves between inlet opening 16 and outlet opening 22, the force of exhaust gas stream 18 accelerates its velocity. This means that the distance between the spheres 24 changes as they move around the chamber 10. This acceleration and change in the distance between the spheres compensates for changes in the pressure and velocity of the exhaust gas stream 18 by allowing expansion of the exhaust gas to take place in the closed loop path between the inlet and the outlet, thus preventing the muffler from exerting back pressure through the exhaust gas stream 18 to an engine connected to the muffler. This ability to prevent back pressure makes this muffler of particular value in use with two cycle internal combustion engines, which are particularly susceptible to power loss from back pressure. It also makes the muffler ideal for use with vacuum cleaners, in which any back pressure causes a corresponding loss in the suction of the vacuum cleaner.

As a sphere 24 passes outlet opening 22, the exhaust gas 18 behind it passes through outlet opening 22 minus substantially all its accompanying sound, and out exhaust gas outlet 20. The sphere 24 then decelerates as it passees around the closed loop of chamber 10 to exhaust gas inlet opening 16. T0 at least a limited extent, the exhaust gas stream 18 from inlet opening 16 appears to pull the spheres 24 behind the inlet opening forward into the stream 18, due to a slight pressure differential between these points in the closed loop chamber 10. Also, a limited amount of the exhaust gas stream 18 will continue around the closed loop path chamber 10 with the spheres 24, and provide some force on them, again due to slight pressure differentials in chamber 10.

It should be noted that the inlet and outlet openings 16 and 22 are located on the inside of the annular closed loop chamber 10. This placement assures that these openings will not interfere with the movement of the spheres 24 around chamber 10, since centrifugal force causes the spheres 24 to roll along the outer wall 12 of chamber 10, as indicated by arrows 28.

FIG. 3 shows another embodiment of the invention in which the shape of the closed loop chamber 10 is modified to help minimize the effect of weight shifts in the muffler as the spheres 24 move around chamber 10. As shown, the chamber 10 maybe considered divided into a left half 30 and a right half 32 for purposes of this explanation. Left half 30 has a smaller radius of curvature R than right half 32, giving the right half 32 a flattened appearance compared with left half 30. It should also be noted that the portion of chamber 10 between exhaust gas inlet 14 and exhaust gas outlet 20 occupies a larger proportion of the closed loop of chamber 10 than in the embodiment of FIG. 1. These modifications mean that there is considerably less shhift in weight in the muffler as the spheres move around chamber 10 that with the embodiment of FIG. 1. This embodiment may therefore be used as a substitute for providing a larger number of spheres 24 to minimize the effect of weight shifts with movement of the spheres, in those situations where a lack of change in the weight distribution is important.

FIG. 4 represents another embodiment of the invention, in which four closed loop chambers 10 of the type represented in FIG. 1 are connected in series by exhaust gas inlets and outlets 14, 20, 34, 36, 38. In this embodiment, the four closed loop chambers 10 taken together constitute the chamber of the muffler. The operation of this embodiment is essentially the same as that of FIG. 1, except that a single sphere 24 may be utilized in each of the chambers 10, if desired. This is possible because, with this arrangement, there will always be at least one sphere 24 between inlet 14 to the first closed loop chamber 10 and outlet 38 from the fourth closed loop chamber 10 in each possible direction of sound travel. Of course, more than one sphere 24 may be used in each closed loop chamber 10 of this embodiment, in the manner of the FIG. 1 embodiment, if desired. Such a series connected arrangement may be of particular advantage when dealing with an especially noisy exhaust gas stream.

It should be apparent to the art skilled that a variety of modifications of the above embodiments can be made within the scope of the claims appended hereto. For example, cylinders could be utilized in place of the spheres 24. The spheres might be made of sintered aluminum or magnesium, rather than being hollow. The shape of the exhaust gas inlets and outlets could be changed to increase or decrease the velocity of the exhaust gas stream 18 in chamber 10. Where the ability of the spheres 24 to assume varying distances from each other to compensate for variations in exhaust gas stream 18 and eliminate back pressure is not important, spheres 24 could be caged in the manner of conventional ball bearings, so that they will move around the closed loop chamber in a predetermined distance relationship. It is intended that these and other changes in form and details within the scope and spirit of the claims appended hereto be considered as part of this invention.

It should now be apparent that an improved muffler capable of achieving the stated objects of the invention has been provided. Use of members movable by an exhaust gas stream around a closed loop path gives a dynamic muffler without the need for bearings with their attendant problems in a muffler environment. In its preferred form, the movable members of the muffler are free to alter their distance relationship to each other as they move around the closed loop path, and thus eliminate back pressure on an engine to which the muffler is connected. While the advantages ofa muffler in accordance with this invention make it of particular value with two cycle internal combustion engines, its reliability and simplicity of construction should give it application in a wide variety of other uses in which effective sound deadening of an exhaust gas stream with little or no back pressure is desired.

What is claimed is:

1. A muffler comprising:

A. a chamber in the form of a closed loop path having a given cross-sectional area,

B. an inlet to said chamber for exhaust gas,

C. an outlet from said chamber for the exhaust gas,

and

D. a plurality of objects rollable in said chamber around said closed loop path, said objects being dimensioned to substantially encompass the crosssectional area of said path.

2. The muffler of claim 1 in which said objects are spherical in shape.

3. The muffler of claim 2 in which said spherical objects are hollow metal balls.

4. A muffler comprising:

A. a chamber in the form ofa closed loop path having a given cross-sectional area,

B. an inlet to said chamber for exhaust gas,

C. an outlet from said chamber for the exhaust gas,

and

D. a plurality of objects movable in said chamber around said closed loop path, said objects being dimensioned to substantially encompass the crosssectional area of said path, said objects being freely movable within said closed loop path with respect to one another, whereby a change in the distance of said objects from one another compensates for variations in an exhaust gas stream.

5. The muffler of claim 4 in which said objects are spherical in shape.

6. The muffler of claim 5 in which said objects are hollow metal balls.

7. A muffler comprising:

A. a chamber including at least one closed loop path having a given cross-sectional area.

B. an inlet to said chamber for exhaust gas,

C. an outlet from said chamber for the exhaust gas,

and

D. a plurality of objects in said chamber freely rollably movable around the at least one closed loop path in response to force exerted by the exhaust gas, said objects being dimensioned to substantially encompass the cross-sectional area of the at least one closed loop path.

8. The muffler of claim 7 in which said chamber comprises a plurality of closed loop paths serially connected by their inlets and outlets, each of said closed loop paths containing at least one of said objects.

9. The muffler of claim 8 in which said objects are spherical in shape.

10. The muffler of claim 9 in which said spherical objects are hollow metal balls.

11. The muffler of claim 7 in which a sufficient number of said objects is provided to assure the presence of at least one said object between said inlet and said outlet for each direction of travel around said closed loop path between said inlet and said outlet.

12. A muffler comprising:

A. a chamber including at least one closed loop path having a given cross-sectional area,

B. an inlet to said chamber for exhaust gas,

C. an outlet from said chamber for the exhaust gas,

and

D. a plurality of objects in said chamber freely movable around the at least one closed loop path in response to force exerted by the exhaust gas, said objects being dimensioned to substantially encompass the cross-sectional area of the at least one closed loop path, the at least one closed loop path being formed from two separate portions having a different radius of curvature, with said inlet and said outlet being connected to the portion having the lesser radius of curvature. 

1. A muffler comprising: A. a chamber in the form of a closed loop path having a given cross-sectional area, B. an inlet to said chamber for exhaust gas, C. an outlet from said chamber for the exhaust gas, and D. a plurality of objects rollable in said chamber around said closed loop path, said objects being dimensioned to substantially encompass the cross-sectional area of said path.
 2. The muffler of claim 1 in which said objects are spherical in shape.
 3. The muffler of claim 2 in which said spherical objects are hollow metal balls.
 4. A muffler comprising: A. a chamber in the form of a closed loop path having a given cross-sectional area, B. an inlet to said chamber for exhaust gas, C. an outlet from said chamber for the exhaust gas, and D. a plurality of objects movable in said chamber around said closed loop path, said objects being dimensioned to substantially encompass the cross-sectional area of said path, said objects being freely movable within said closed loop path with respect to one another, whereby a change in the distance of said objects from one another compensates for variations in an exhaust gas stream.
 5. The muffler of claim 4 in which said objects are spherical in shape.
 6. The muffler of claim 5 in which said objects are hollow metal balls.
 7. A muffler comprising: A. a chamber including at least one closed loop path having a given cross-sectional area. B. an inlet to said chamber for exhaust gas, C. an outlet from said chamber for the exhaust gas, and D. a plurality of objects in said chamber freely rollably movable around the at least one closed loop path in response to force exerted by the exhaust gas, said objects being dimensioned to substantially encompass the cross-sectional area of the at least one closed loop path.
 8. The muffler of claim 7 in which said chamber comprises a plurality of closed loop paths serially connected by their inlets and outlets, each of said closed loop paths containing at least one of said objects.
 9. The muffler of claim 8 in which said objects are spherical in shape.
 10. The muffler of claim 9 in which said spherical objects are hollow metal balls.
 11. The muffler of claim 7 in which a sufficient number of said objects is provided to assure the presence of at least one said object between said inlet and said outlet for each direction of travel around said closed loop path between said inlet and said outlet.
 12. A muffler comprising: A. a chamber including at least one closed loop path having a given cross-sectional area, B. an inlet to said chamber for exhaust gas, C. an outlet from said chamber for the exhaust gas, and D. a plurality of objects in said chamber freely movable around the at least one closed loop path in response to force exerted by the exhaust gas, said objects being dimensioned to substantially encompass the cross-sectional area of the at least one closed loop path, the at least one closed loop path being formed from two separate portions having a different radius of curvature, with said inlet and said outlet being connected to the portion having the lesser radius of curvature. 